16,613 research outputs found
Molecular Model of the Contractile Ring
We present a model for the actin contractile ring of adherent animal cells.
The model suggests that the actin concentration within the ring and
consequently the power that the ring exerts both increase during contraction.
We demonstrate the crucial role of actin polymerization and depolymerization
throughout cytokinesis, and the dominance of viscous dissipation in the
dynamics. The physical origin of two phases in cytokinesis dynamics ("biphasic
cytokinesis") follows from a limitation on the actin density. The model is
consistent with a wide range of measurements of the midzone of dividing animal
cells.Comment: PACS numbers: 87.16.Ka, 87.16.Ac
http://www.ncbi.nlm.nih.gov/pubmed/16197254
http://www.weizmann.ac.il/complex/tlusty/papers/PhysRevLett2005.pd
Reef Rescue Marine Monitoring Program: Using remote sensing for GBR-wide water quality. Final report for 2012/13 activities
This report delivers management relevant information of flood events and inshore water quality compliance based on tailored temporal and spatial analysis of remote sensing data, carried out by CSIRO as part of the Reef Rescue Marine Monitoring Program (MMP) from 2005 to 2013
Air hydrodynamics of the ultrafast laser-triggered spark gap
We present space and time resolved measurements of the air hydrodynamics
induced by ultrafast laser pulse excitation of the air gap between two
electrodes at high potential difference. We explore both plasma-based and
plasma-free gap excitation. The former uses the plasma left in the wake of
femtosecond filamentation, while the latter exploits air heating by
multiple-pulse resonant excitation of quantum molecular wavepackets. We find
that the cumulative electrode-driven air density depression channel initiated
by the laser plays the dominant role in the gap evolution leading to breakdown
Helium-3 and Helium-4 acceleration by high power laser pulses for hadron therapy
The laser driven acceleration of ions is considered a promising candidate for
an ion source for hadron therapy of oncological diseases. Though proton and
carbon ion sources are conventionally used for therapy, other light ions can
also be utilized. Whereas carbon ions require 400 MeV per nucleon to reach the
same penetration depth as 250 MeV protons, helium ions require only 250 MeV per
nucleon, which is the lowest energy per nucleon among the light ions. This fact
along with the larger biological damage to cancer cells achieved by helium
ions, than that by protons, makes this species an interesting candidate for the
laser driven ion source. Two mechanisms (Magnetic Vortex Acceleration and
hole-boring Radiation Pressure Acceleration) of PW-class laser driven ion
acceleration from liquid and gaseous helium targets are studied with the goal
of producing 250 MeV per nucleon helium ion beams that meet the hadron therapy
requirements. We show that He3 ions, having almost the same penetration depth
as He4 with the same energy per nucleon, require less laser power to be
accelerated to the required energy for the hadron therapy.Comment: 8 pages, 3 figures, 1 tabl
Evaluating Workplace Mandates with Flows versus Stocks: An Application to California Paid Family Leave
Abstract. Employer mandates often have small effects on wages and employment. Such effects should be most evident using data on employment transitions and wages among new hires. Quarterly Workforce Indicators (QWI) provides county by quarter by demographic group data on the number and earnings of new hires, separations, and recalls (extended leaves). The QWI is used to examine the effects of California’s 2004 paid family leave (CPFL) program, comparing outcomes for young women in California to those for other workers within and outside of California. CPFL had little effect on earnings for young women, but increased separations, hiring, and worker mobility. JEL codes: J32 (nonwage labor costs), J38 (public policy
Evaluating Workplace Mandates with Flows versus Stocks: An Application to California Paid Family Leave
Some remarks on the visible points of a lattice
We comment on the set of visible points of a lattice and its Fourier
transform, thus continuing and generalizing previous work by Schroeder and
Mosseri. A closed formula in terms of Dirichlet series is obtained for the
Bragg part of the Fourier transform. We compare this calculation with the
outcome of an optical Fourier transform of the visible points of the 2D square
lattice.Comment: 9 pages, 3 eps-figures, 1 jpeg-figure; updated version; another
article (by M. Baake, R. V. Moody and P. A. B. Pleasants) with the complete
solution of the spectral problem will follow soon (see math.MG/9906132
Lattice simulations with eight flavors of domain wall fermions in SU(3) gauge theory
We study an SU(3) gauge theory with Nf=8 degenerate flavors of light fermions
in the fundamental representation. Using the domain wall fermion formulation,
we investigate the light hadron spectrum, chiral condensate and electroweak S
parameter. We consider a range of light fermion masses on two lattice volumes
at a single gauge coupling chosen so that IR scales approximately match those
from our previous studies of the two- and six-flavor systems. Our results for
the Nf=8 spectrum suggest spontaneous chiral symmetry breaking, though fits to
the fermion mass dependence of spectral quantities do not strongly disfavor the
hypothesis of mass-deformed infrared conformality. Compared to Nf=2 we observe
a significant enhancement of the chiral condensate relative to the symmetry
breaking scale F, similar to the situation for Nf=6. The reduction of the S
parameter, related to parity doubling in the vector and axial-vector channels,
is also comparable to our six-flavor results
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